How can I make an object render with a wireframe in the game engine?
You want to create a wireframe material. A quick 'n' dirty way to do generate a wireframe texture is described below:

Unwrap your model. If you don't know how to do this simply select everything and press CtrlE &gt; Mark Seam.

Press U &gt; Unwrap.

Open up a UV/Image editor:


Click UVs &gt; Export UV Layout. Remember where you save this image.

Press AltO to open a texture, then select the saved image.

Tada!



You may want to remove the transparency in an image editor if you want your model to be opaque.